In swimming there has existed a controversy over whether the propulsion that is derived from swimming is caused by Bernoulli's theorem (that explains lift forces) or Newton's principles (that explain both lift and drag forces). This article is about the joice between these two models. Conclusion: Attempting to explain swimming forces because of Bernoullian lift is inappropriate. Ascriptions to the shape of a swimmer's hand surface as being an airfoil are misleading. Lift forces in swimming are primarily caused by the pitch (angle of attack) of the hand, not shape. Thus, Bernoulli's principle is not appropriate for explaining the major forces in swimming propulsion but Newton's are. Bernoulli's theorem only explains lift while Newton's principles explain lift and drag. Lift is only part of the total force "package" and does not always point in the direction of intended travel. Implication. It is more appropriate to explain and understand swimming forces by invoking Newtonian principles than by using Bernoulli's theorem. The fact that the forearm and hand cannot change shape to accommodate different speeds is the weakness in the Bernoulli argument. As well, the speeds attained in swimming are quite low and not conducive to good Bernoullian lift, even if shape alterations were possible.
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